Organic Chemistry

Question 1

what are the uses for aclohols?

Answer 1

as fuels – ethanol is added to petrol
solvents – in perfume where the alcohol evaporates
ethanol in alcoholic drinks

Question 2

how can ethanol be oxidised?

Answer 2

1. burning in air or oxygen (complete combustion)
2. reaction with oxygen in air to form ethanoic acid (by microbes)
3. heating with potassium dichromate VI in dilute sulfuric acid to form ethanoic acid colour change is orange to green

Question 3

how can ethanol be manufactured & what conditions are needed?

Answer 3

1. react ethene with steam (hydration of ethene)
   phosphoric acid catalyst
   temperature 300C
   pressure 60-70 atm
2. fermentation of glucose
   absence of air (anaerobic conditions so yeast anaerobically respires)
   optimum temperature 30C
   enzymes in yeast

Question 4

what are the advantages & disadvantages of fermentation?

Answer 4

advantages:
renewable raw materials

disadvantages:
batch process
slow
produces impure ethanol - 10%

Question 5

how is ethanol a biofuel & what are the advantages?

Answer 5

renewable substance = can be replaced
it is carbon neutral: photosynthesis, fermentation, combustion
clean flame

Question 6

what are the advantages & disadvantages of hydration?

Answer 6

advantages:
continuous process
very fast - seconds
produces more pure ethanol - 99%

disadvantages: non-renewable raw materials
impurities are toxic

Question 7

what type of acids are carboxylic acids & explain?

Answer 7

weak acid
small fraction of molecules break down to form H+ ions (ionise) when added to water

Question 8

what makes an acid strong?

Answer 8

all molecules break down to form H+ ions (ionise) when added to water

Question 9

describe reaction of aqueous solutions of carboxylic acids with metals & metal carbonates

Answer 9

carboxylic acid + metal –> salt + hydrogen
fizzes gently

carboxylic acid + metal carbonate –> salt + carbon dioxide + water

Question 10

what is vinegar?

Answer 10

aqueous solution containing ethanoic acid

Question 11

what is the functional group of esters?

Answer 11

-COOC

Question 12

how is ethyl ethanoate formed?

Answer 12

ethanol + ethanoic acid + concentrated sulfuric acid catalyst & warm

Question 13

describe a method to prepare a sample of an ester e.g. ethyl ethanoate

Answer 13

1. put 10 drops of concentrated ethanoic acid into a boiling tube & add 10 drops of ethanol
2. separately smell ethanol & ethanoic acid
3. add 2 drops of concentrated sulfuric acid to the vertical boiling tube
4. warm mixture (do not boil) for 2 mins
5. add sodium carbonate solution to neutralise excess ethanoic acid so when it doesn’t fizz as much you add more
6. smell the product & note observations

Question 14

what are the characteristics of esters?

Answer 14

volatile
distinctive fruity smells

Question 15

what are the uses of esters?

Answer 15

food flavourings
perfumes

Question 16

what is an addition polymer?

Answer 16

long-chain molecules formed by joining many small molecules (monomers) with no additional products

Question 17

how do you draw repeating unit/structure of a polymer?

Answer 17

1. change C=C to C-C
2. put bonds on both sides of C-C
3. brackets through bonds at the side
4. maximum 2 Cs across the middle

Question 18

what are the problems in the disposal of addition polymers?

Answer 18

they are inert & cannot biodegrade so putting them in landfills does not actually dispose of them

when burned, toxic gases are produced

Question 19

what are condensation polymers?

Answer 19

long-chain molecules formed by joining lots of small molecules (monomers) with additional products (e.g. water) also formed

Question 20

in condensation polymerisation what are the reagents & products?

Answer 20

diol + dicarboxylic acid –> polyester + water

Question 21

what polyesters are biodegradable?

Answer 21

biopolyesters